A knife sharpener is a must-have for your kitchen if you don't want to end up hacking away with a blunt kitchen knife.
In March 2021 we tested nine handheld knife sharpeners from Lakeland, Joseph Joseph, Robert Welch and more. As well as comparing these against each other to discover the best knife sharpener, we also compared them with a traditional whetstone used for sharpening knives to see which gives better results.
Pricing and availability last checked 01 September 2021.
The best knife sharpeners
Only logged-in Which? members can view the knife-sharpener test results. If you're not a member, or not yet logged in, you'll see an alphabetically ordered list of the handheld knife sharpeners we tested.
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The Robert Welch sharpener is arguably one of the more elegantly designed knife sharpeners we tested.
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Three things we learned testing knife sharpeners
A whetstone combined with a honing steel gives the best results (better than knife sharpeners). After our main testing, we used a honing steel on all the knives we'd sharpened and then re-did our paper test with them. We found that they all got better results. But (and it's a big but) only use this method if you know what you're doing. Otherwise, you risk damaging the cutting edge of your knife.
When the sharpener has more than one setting, the coarse setting is the sharpener and the fine one is normally similar to a honing steel.
Handheld sharpeners are designed to keep your blade fresh, and you should use them to top up the blade after every few hours of use. They aren't great with fully dulled knives; that's what a whetstone is for.
How to use a knife sharpener
If your knife has more than one setting, select 'coarse' for very blunt knives that need to be re-sharpened. The fine or honing setting is for everyday knife maintenance.
Put the blade into your knife sharpener at the point where the knife blade meets the handle.
Pull the knife blade along the sharpening steel towards your body, with enough gentle force that you can hear a grinding noise.
Repeat this action three to six times. You can go for three if your blade is just a bit dull, and more if it's blunter.
As most knife blades aren't straight, you don't want to just pull it straight through the sharpener. Instead, follow the contour of the blade as you pull it through. If you stop hearing the grinding noise, or the knife starts to feel too difficult to pull through, then you're not following the contour correctly.
If your knife sharpener has a fine or honing setting, run it through that once or twice once you've finished with the coarse setting. Do this in the same way, but with less force. To keep your knife sharp, use the fine setting once after every couple of hours of use.
Rinse the knife and dry it.
Some knife sharpeners allow you to replace the sharpener wheel when needed; others don't. Popular knife and knife-sharpener manufacturer Robert Welch recommends you change the sharpening wheel after 12-24 months, depending on the frequency of use, to maintain your knife's cutting edge to a high standard.
How to use a whetstone
Whetstones are a different way of sharpening knives. They're sometimes known as sharpening stones, and are essentially a two-sided block of coarse stone (one side more coarse than the other) and a base/holder.
We tried one out alongside the knife sharpeners we tested to see how the two compared, and discovered that a whetstone is much harder to use. To get a good result you need skill and practice, plus considerable patience.
Once you've mastered a whetstone it does sharpen knives brilliantly, but you'll end up with a mess wherever you choose to use it, which you won't see with a knife sharpener.
Soak the whetstone for around 10 minutes (or the time it says with the instructions it came with).
Start with the coarser of the two sides facing up.
Hold the knife at an approx 22-degree angle to the stone. How the heck do you measure that, you might ask? Well, 90 degrees is your knife placed on the stone as if you were going to cut through it. Tilt the knife halfway between that and the whetstone and you'll be at 45 degrees. Then tilt it halfway between that and the stone and you'll be at around the correct angle you need.
Apply moderate pressure and slide the knife forwards at that angle 10 times.
Switch to the fine grit side and stroke the knife down the stone at a 22-degree angle 10 times.
Finish with a honing steel for best results. Rinse and dry the knife. You may also need to clean up the area around the whetstone.
How to use a honing steel
A honing steel (sometimes also called a honing rod or a sharpening steel) doesn't exactly sharpen your knife. What a honing steel does is to realign the cutting edge to smooth out microscopic bumps and jagged edges.
To use a honing steel:
Hold the steel with the tip resting on your countertop.
Place the heel of the blade (the bit where it connects to the handle) against the steel, with the knifepoint angled slightly upwards.
Tilt the blade to around a 15-degree angle.
Keeping it at that angle, pull the knife down the honing steel while pulling the handle towards you.
Do this on both sides of the blade around eight to 10 times.
A rasping sound means you're applying too much pressure. It should be more like a 'ting' sound you're hearing.
How often should you sharpen a knife?
Little and often. If you hone a knife frequently then you shouldn't need to sharpen it as much. Hone it for every couple of hours of use.
What is a sharpener doing to your blade?
It's essentially taking away a bit of the metal each time, but it's so little that you won't notice.
How to test how sharp your knife is
There are two easy ways to test the sharpness of your knife.
Shine a light directly over the cutting edge of the blade. Any areas of reflected light show parts of the cutting edge that have been dulled.
Slice the knife through a piece of A4 paper (landscape). A fully sharpened knife will go through it as if it was warm butter.
How we tested knife sharpeners
First, we blunted 10 identical knives using a whetstone.
We used the Gourmet X30 chef's knife from ProCook.
We then examined each of the knives to make sure we were satisfied that each was blunted to the same degree.
We used one of each of these knives to test each knife sharpener, following the manufacturers' instructions.
Ease of use
We rated each knife sharpener on how easy it was to use for sharpening a knife.
Condition of the blade after sharpening
We examined the cutting edges of each blade, checking for any still-blunt areas. If there was no reflected light across the cutting edge of a blade, we gave it a higher rating.
We took each sharpened knife and used it to slice the following items in half:
Paper – starting at the heel of the knife, we dragged it down through the paper in a slicing motion.
Butternut squash – we cut top to bottom lengthways, putting our weight on the blade's handle.
Tomato – we sliced through it horizontally, with one hand on the knife and the other on the top of the tomato.
How we chose the knife sharpeners
We investigated the most popular and bestselling brands from national retailers. We chose one handheld knife sharpener per brand in our selection.